Ring structure is a kind of structural form formed in different geological times. A complete ring structure consists of inner ring

middle ring and outerring. The inner ring is the tractive-tensile area with basement arched upward.Normal faults and volcanic rocks developed and fault-subsided basin were formed there. The middle and outer rings are mainly compressive areas with folded arcs

granite arcs

overthrusts and nappes. More than ten ring structures are found in North China. They compose four NW-SE trending ring structural chains which are the traces of mantle heat source acted on shifting land block during the Meso-Cenozoic. The fault subsided basin formed in the late evolution stage of the raising of mantle heat source and crust expansion. If it bas proper size

depth and sedi-ments of great thickness

and also has source-reservoircap rock assemblage.it will certainly develop into a hydrocarbon basin. Oil and gas fields have been found in three ring structures and oil shows are discovered in another one in north China. All of them are related to Meso-Cenozoic fault-depressed basin.